Viruses of genus coronavirus and genus rotavirus may induce various diseases of livestock, and particularly porcine viral diarrhea induced by a porcine transmissible gastroenteritis virus, a porcine epidemic diarrhea virus and/or a porcine rotavirus and the like has become one of the severest diseases threatening pig production.
Until now, there is no effective prevention or treatment method available for the porcine viral diarrhea, for the following reasons:
In one aspect, effective and reliable vaccine has not been successfully developed. In recent years, a separated porcine epidemic diarrhea virus strain has a gene homology of about 86-98% with CV777, which indicates great difficulty in vaccine research and development. In fact, a commercially available PED vaccine or a PED/TGE bivalent vaccine and a PED/TGE/PoRV trivalent vaccine under research and development that have been approved in China, all do not achieve an ideal protection rate on the epidemic diarrhea. The PED vaccine approved for market sale in the United States in 2014 is also subject to such problem. Currently, all around the world, especially in the United States, a feedback technique is widely applied to treat such disease, which is also a helpless choice. First, the feedback needs epidemic materials, that is, materials for the feedback may be obtained only in the case of occurrence of the disease, and once the disease occurs, a great loss may hardly be avoided. Second, an effect of the feedback is not definite, and the disease may recur two or three months later. Third, the feedback may cause biosafety risks, that is, outbreaks of other diseases may be introduced to swine herds, and thus an even greater loss may be caused.
In another aspect, the conventional drugs for prevention or treatment of the diseases do not have a definite effect. For example, none of a interferon, yolk antibody, thymosin peptide and the like achieves an ideal effect on the porcine viral diarrhea. Study made by Kim et al. reveals that the antiviral drug, Ribavirin, is capable of inhibiting replication of PEDV (Virus Research (2013), 171(1), 44-53). However, regulations and laws all around the world prohibit using human antiviral drugs for food animals, and use of the antiviral drugs such as Ribavirin, amantadine and the like is prohibited in prevention and treatment of the porcine epidemic diarrhea. Study made by Lee et al. finds that a polysaccharide extracted from a ginkgo testa has inhibition of PEDV in vitro and has an activity superior to that of Ribavirin, as a potential anti-PEDV substance (Virus Research (20158), 195, 148-152). However, such study achievement is only limited to experiments in vitro, and the effect in vivo still needs to be proved by using a large number of experiments. Chinese patent applications 2013100930843 and 201310147391.5 disclose treatment and prevention of the porcine epidemic diarrhea by using combined Chinese herbal medicine after being smashed directly. Generally, this treatment or prevention method takes a slower and limited effect, and particularly makes no effect on newborn piglets.
In a further aspect, clinically, a specific dose of a disinfectant such as povidone iodine and the like has ever been orally administered to the diseased piglets for treatment of the epidemic diarrhea, which has a certain effect and improves a survival rate by 5-10%. However, prognosis of the survived suckling piglets is poor, and the piglets grow slowly. Clinically, a supportive therapy is generally employed to help the diseased pigs to resist the disease, i.e. relief of symptoms and correction of dehydration of the diseased pigs are made by using a method of orally feeding water containing oral rehydration salts (ORS) or intraperitoneally supplementing seepage such as glucose electrolyte and the like. This method achieves certain effects on weaned piglets, care pigs and adult pigs, but has a tiny effect on low-day-aged suckling piglets. In US patent application US2014/0287065A1, water containing electrolytes such as sodium hypochlorite, sodium hydroxide and the like is orally administered to pigs to reduce an incidence of dehydration among PEDV-infected grown-up pigs, but the patent fails to provide data convincing the effect on the low-day-aged suckling piglets.
Taurine, also referred to as β-aminoethanesulfonic acid, was originally separated from calculus bovis and named by this. Pure taurine is a colorless or white oblique crystal, and odorless. Taurine has a stable chemical property and is a non-protein amino acid containing sulfur, which is existent in vivo in a free state and is not engaged in biosynthesis of the protein in vivo. As disclosed in the prior arts, taurine can be used for a dietary supplement or a drug. The use of taurine as a drug includes: preventing and treating cardiovascular diseases, exerting a cardiac effect and resisting cardiac arrhythmia, lowering blood fat and cholesterol, lowering blood pressure, lowering blood sugar, strengthening liver and benefiting gallbladder, and effects such as antipyretic effect, analgesic effect, anti-inflammation and the like. Taurine is also commonly used as a pharmaceutical auxiliary material and is added to a drug formulation for strengthening the effect of a major medicine, improving a lack of taurine for patients and enhancing cell protection. Chinese patent 201010505721.X discloses a strengthening effect of taurine on major medicines which are andrographolide and extract of Hedyotis diffusa. Chinese patent application 201310072382.4 discloses a synergistic effect of taurine and the major medicine, an interferon, for inhibiting activities of vesicular stomatitis virus as well as murine encephalomyocarditis virus and for a cell protection effect thereof. In addition, it has been formerly reported that a mixture of taurine, compound anthocyanidin and Aspirin can be used for the treatment of porcine reproductive and respiratory syndrome; and astragalus and taurine can lower a death rate of BALB/c mice with myocarditis induced by infection of Coxsackievirus B3. However, the prior arts do not report that taurine is used for prevention and/or treatment of diseases induced by viruses of the genus coronavirus, and especially do not report that taurine is used for prevention and treatment of the porcine viral diarrhea.